Natural gas has been used as fuel for internal combustion engines in consist locomotives. Because natural gas has a lower volumetric energy density than traditional fuels, such as diesel and gasoline, the natural gas used by the locomotives is generally only practical to store in a liquefied state (“LNG”). At atmospheric pressures, the natural gas must be chilled to below about −160° C. to remain in liquid form. Consists having LNG-fueled locomotives store the LNG in insulated tank cars (a.k.a., tender cars) that are towed by the locomotive.
A locomotive's main engine drives a generator to produce electricity used to power traction motors that propel the locomotive. The electricity can also be used to power one or more auxiliary loads (e.g., lights, air conditioning, etc.) of the consist. Given the auxiliary loads' dependence on electricity generated by the main engine, the main engine is generally kept operational even when the locomotive is stopped. In this situation, powering the auxiliary loads with the main engine can result in low fuel economy. In addition, powering the auxiliary loads when the locomotive is traveling can reduce a capacity of the main engine to power the traction motors.
One method of improving fuel economy of a consist is described in U.S. Patent Publication No. 2010/0186619 (“the '619 publication”) of Kumar that published on Jul. 29, 2010. The '619 publication describes locomotives and rail cars that have the capacity to generate electric power from dynamic braking, to store the power, and to reuse the power at a later time during motoring. The energy can be used to power auxiliary loads, as well as traction motor/propulsion systems, until the energy stores are depleted. This capability may help to improve the fuel economy of a consist.
Although the system of the '619 publication may improve fuel economy to some degree, the amount of improvement may be limited. In particular, the system of the '610 patent may function only for short distances and/or in particular terrain. That is, because the system of the '619 publication uses energy stored from dynamic braking, its energy reservoir may be transitory and dependent on the type of terrain being traversed by the consist. Long stretches of travel across areas that do not require significant dynamic braking could threaten to quickly deplete such an electric energy reserve.
The system of the present disclosure solves one or more of the problems set forth above and/or other problems with existing technologies.